Posts Tagged ‘Big Bang’

By Stephanie Pappas

The Big Bang is commonly thought of as the start of it all: About 13.8 billion years ago, the observable universe went boom and expanded into being.

But what were things like before the Big Bang?

Short answer: We don’t know. Long answer: It could have been a lot of things, each mind-bending in its own way.

The first thing to understand is what the Big Bang actually was.

“The Big Bang is a moment in time, not a point in space,” said Sean Carroll, a theoretical physicist at the California Institute of Technology and author of “The Big Picture: On the Origins of Life, Meaning and the Universe Itself” (Dutton, 2016).

So, scrap the image of a tiny speck of dense matter suddenly exploding outward into a void. For one thing, the universe at the Big Bang may not have been particularly small, Carroll said. Sure, everything in the observable universe today — a sphere with a diameter of about 93 billion light-years containing at least 2 trillion galaxies — was crammed into a space less than a centimeter across. But there could be plenty outside of the observable universe that Earthlings can’t see because it’s physically impossible for the light to have traveled that far in 13.8 billion years.
Thus, it’s possible that the universe at the Big Bang was teeny-tiny or infinitely large, Carroll said, because there’s no way to look back in time at the stuff we can’t even see today. All we really know is that it was very, very dense and that it very quickly got less dense.

As a corollary, there really isn’t anything outside the universe, because the universe is, by definition, everything. So, at the Big Bang, everything was denser and hotter than it is now, but there was no more an “outside” of it than there is today. As tempting as it is to take a godlike view and imagine you could stand in a void and look at the scrunched-up baby universe right before the Big Bang, that would be impossible, Carroll said. The universe didn’t expand into space; space itself expanded.

“No matter where you are in the universe, if you trace yourself back 14 billion years, you come to this point where it was extremely hot, dense and rapidly expanding,” he said.

No one knows exactly what was happening in the universe until 1 second after the Big Bang, when the universe cooled off enough for protons and neutrons to collide and stick together. Many scientists do think that the universe went through a process of exponential expansion called inflation during that first second. This would have smoothed out the fabric of space-time and could explain why matter is so evenly distributed in the universe today.

Before the bang

It’s possible that before the Big Bang, the universe was an infinite stretch of an ultrahot, dense material, persisting in a steady state until, for some reason, the Big Bang occured. This extra-dense universe may have been governed by quantum mechanics, the physics of the extremely small scale, Carroll said. The Big Bang, then, would have represented the moment that classical physics took over as the major driver of the universe’s evolution.

For Stephen Hawking, this moment was all that mattered: Before the Big Bang, he said, events are unmeasurable, and thus undefined. Hawking called this the no-boundary proposal: Time and space, he said, are finite, but they don’t have any boundaries or starting or ending points, the same way that the planet Earth is finite but has no edge.

“Since events before the Big Bang have no observational consequences, one may as well cut them out of the theory and say that time began at the Big Bang,” he said in an interview on the National Geographic show “StarTalk” in 2018.

Or perhaps there was something else before the Big Bang that’s worth pondering. One idea is that the Big Bang isn’t the beginning of time, but rather that it was a moment of symmetry. In this idea, prior to the Big Bang, there was another universe, identical to this one but with entropy increasing toward the past instead of toward the future.

Increasing entropy, or increasing disorder in a system, is essentially the arrow of time, Carroll said, so in this mirror universe, time would run opposite to time in the modern universe and our universe would be in the past. Proponents of this theory also suggest that other properties of the universe would be flip-flopped in this mirror universe. For example, physicist David Sloan wrote in the University of Oxford Science Blog, asymmetries in molecules and ions (called chiralities) would be in opposite orientations to what they are in our universe.

A related theory holds that the Big Bang wasn’t the beginning of everything, but rather a moment in time when the universe switched from a period of contraction to a period of expansion. This “Big Bounce” notion suggests that there could be infinite Big Bangs as the universe expands, contracts and expands again. The problem with these ideas, Carroll said, is that there’s no explanation for why or how an expanding universe would contract and return to a low-entropy state.

Carroll and his colleague Jennifer Chen have their own pre-Big Bang vision. In 2004, the physicists suggested that perhaps the universe as we know it is the offspring of a parent universe from which a bit of space-time has ripped off.

It’s like a radioactive nucleus decaying, Carroll said: When a nucleus decays, it spits out an alpha or beta particle. The parent universe could do the same thing, except instead of particles, it spits out baby universes, perhaps infinitely. “It’s just a quantum fluctuation that lets it happen,” Carroll said. These baby universes are “literally parallel universes,” Carroll said, and don’t interact with or influence one another.

If that all sounds rather trippy, it is — because scientists don’t yet have a way to peer back to even the instant of the Big Bang, much less what came before it. There’s room to explore, though, Carroll said. The detection of gravitational waves from powerful galactic collisions in 2015 opens the possibility that these waves could be used to solve fundamental mysteries about the universes’ expansion in that first crucial second.

Theoretical physicists also have work to do, Carroll said, like making more-precise predictions about how quantum forces like quantum gravity might work.

“We don’t even know what we’re looking for,” Carroll said, “until we have a theory.”


The detailed, all-sky picture of the infant universe created from nine years of WMAP data. The image reveals 13.77 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies. The signal from our galaxy was subtracted using the multi-frequency data. This image shows a temperature range of ± 200 microKelvin.CREDIT: NASA/WMAP SCIENCE TEAM

by Jesse Shanahan

In a study published earlier this month, a team of theoretical physicists is claiming to have discovered the remnants of previous universes hidden within the leftover radiation from the Big Bang. Our universe is a vast collection of observable matter, like gas, dust, stars, etc., in addition to the ever-elusive dark matter and dark energy. In some sense, this universe is all we know, and even then, we can only directly study about 5% of it, leaving 95% a mystery that scientists are actively working to solve. However, this group of physicists is arguing that our universe isn’t alone; it’s just one in a long line of universes that are born, grow, and die. Among these scientists is mathematical physicist Roger Penrose, who worked closely with Stephen Hawking and currently is the Emeritus Rouse Ball Professor of Mathematics at Oxford University. Penrose and his collaborators follow a cosmological theory called conformal cyclic cosmology (CCC) in which universes, much like human beings, come into existence, expand, and then perish.

As a universe ages, it expands, and the constituent parts grow farther and farther apart from each other. Consequently, the interactions between galaxies that drive star formation and evolution become rarer. Eventually, the stars die out, and the remaining gas and dust is captured by black holes. In one of his most famous theories, Stephen Hawking proposed that this isn’t the end; black holes might have a way to slowly lose mass and energy by radiating certain particles. So, after many eons, the remaining black holes in the universe would disappear, leaving only disparate particles. Seemingly a wasteland, this end-state eventually mirrors the environment of our universe’s birth, and so, the cycle starts anew.

universe 2
Artist’s logarithmic scale conception of the observable universe with the Solar System at the center, inner and outer planets, Kuiper belt, Oort cloud, Alpha Centauri, Perseus Arm, Milky Way galaxy, Andromeda galaxy, nearby galaxies, Cosmic Web, Cosmic microwave radiation and Big Bang’s invisible plasma on the edge.CREDIT: WIKIPEDIA/PABLO CARLOS BUDASSI

When our universe was very young, before any recognizable components like stars, planets, or galaxies formed, it was filled with a dense, hot soup of plasma. As the universe expanded, it cooled, and eventually, particles could combine to form atoms. Eventually, the interaction and fusion of these atoms resulted in all of the matter that we observe today. However, we can still observe the leftover radiation from that initial, dense period in our universe’s history. This leftover glow, called the Cosmic Microwave Background (CMB), is the oldest electromagnetic radiation, and it fills the entirety of our universe. If the CCC theory were true, then there would be hints of previous universes in our universe’s CMB.

At the end of a universe, when those final black holes dissolve, CCC theory states they should leave behind a signature that would survive the death of that universe and persist into the next. Although not definitive proof of previous universes, detecting that signature would be strong evidence in support of CCC theory. In searching for these “Hawking points”, cosmologists face a difficult obstacle as the CMB is faint and varies randomly. However, Penrose is claiming that a comparison between a model CMB with Hawking points and actual data from our CMB has proven that Hawking points actually exist. If true, this would be the first-ever detection of evidence from another universe.

Unfortunately, as groundbreaking as this discovery seems, the scientific community has largely dismissed it. One of the fundamental characteristics of the CMB is that, although it has patterns, the variations are entirely statistically random. In fact, Penrose’s former collaborator, Stephen Hawking, spotted his own initials in the CMB while others have found a deer, a parrot, and numerous other recognizable shapes in the noise. Similarly, the Wilkinson Anisotropy Microscope Probe that mapped the CMB released an interactive image where you can search for familiar shapes and patterns. An avoidable result of both these random fluctuations and the sheer size of the CMB is that if scientists look hard enough, they can find whatever pattern they need, like the existence of Hawking points, perhaps. Another criticism of Penrose’s claim is that if CCC theory holds true, our universe should have tens of thousands of Hawking points in the CMB. Regrettably, Penrose could find only about 20.

Still, the possibility of alternate universes, whether long-dead or existing in parallel to our own, is tantalizing. Many other theories also claim to find traces of other universes hiding in the patterns of the CMB as well. Although it sounds like science fiction, we are left to wonder: is this just the cosmological equivalent of seeing shapes in random clouds or will scientists one day discover that we are one among many infinite universes?

Jesse Shanahan is an astrophysicist, EMT, and science communicator. For more space and language news, follow her on Twitter here.

By Jeffrey Bennett

It has been exactly 100 years since Albert Einstein presented his theory of general relativity to an audience of scientists on November 25, 1915. While virtually everyone has heard of Einstein and his theory, very few people have any idea of what the theory actually is.

This is a shame, not only because there is a great public thirst for understanding of it, but also because relativity is important, for at least four major reasons.

General relativity provides our modern understanding of space, time and gravity — which means it’s crucial to almost everything we do in physics and astronomy. For example, you cannot understand black holes, the expansion of the universe or the Big Bang without first understanding the basic ideas of relativity. Though few people realize it, Einstein’s famous equation E = mc2 is actually part of the theory of relativity, which means that relativity also explains how the sun shines and how nuclear power works.

A second reason everyone should know about relativity lies in the way it changes our perception of reality. Relativity tells us that our ordinary perceptions of time and space are not universally valid. Instead, space and time are intertwined as four-dimensional space-time.

In our ordinary lives, we perceive only three dimensions—length, width and depth—and we assume that this perception reflects reality. However, in space-time, the four directions of possible motion are length, width, depth and time. (Note that time is not “the” fourth dimension; it is simply one of the four.)

Although we cannot picture all four dimensions of space-time at once, we can imagine what things would look like if we could. In addition to the three spatial dimensions of space-time that we ordinarily see, every object would be stretched out through time. Objects that we see as three-dimensional in our ordinary lives would appear as four-dimensional objects in space-time. If we could see in four dimensions, we could look through time just as easily as we look to our left or right. If we looked at a person, we could see every event in that person’s life. If we wondered what really happened during some historical event, we’d simply look to find the answer.

To see why this is so revolutionary, imagine that you met someone today who deeply believed that Earth is the center of the universe. You would probably feel sorry for this person, knowing that his or her entire world view is based on an idea disproven more than 400 years ago.

Now imagine that you met someone who still believed that time and space are independent and absolute — which, of course, describes almost everyone — even though we’ve known that’s not the case for a century now. Shouldn’t we feel equally sorry for all who hold this modern misconception?

It seems especially unfortunate once you realize that the ideas of relativity are not particularly difficult to understand. Indeed, I believe we could begin teaching relativity in elementary school in much the same way that we teach young children about the existence of atoms, even though few will ever study quantum mechanics.

My third reason for believing relativity is important lies in what Einstein’s discovery tells us about human potential. The science of relativity may seem disconnected from most other human endeavors, but I believe Einstein himself proved otherwise. Throughout his life, Einstein argued eloquently for human rights, human dignity and a world of peace and shared prosperity. His belief in underlying human goodness is all the more striking when you consider that he lived through both World Wars, that he was driven out of Germany by the rise of the Nazis, that he witnessed the Holocaust that wiped out more than six million of his fellow Jews, and that he saw his own discoveries put to use in atomic bombs.

No one can say for sure how he maintained his optimism in the face of such tragedies, but I see a connection to his discovery of relativity. Einstein surely recognized that a theory that so challenged our perceptions of reality might have been dismissed out of hand at other times in history, but that we now live in a time when, thanks to the process that we call science, the abundant evidence for relativity allowed for its acceptance.

This willingness to make judgments based on evidence shows that we are growing up as a species. We have not yet reached the point where we always show the same willingness in all our other endeavors, but the fact that we’ve done it for science suggests we have the potential.

Finally, on a philosophical level, relativity is profound. Only about a month before his death in 1955, Einstein wrote: “Death signifies nothing … the distinction between past, present and future is only a stubbornly persistent illusion.” As this suggests, relativity raises interesting questions about what the passage of time really means.

Because these are philosophical questions, they do not have definitive answers, and you will have to decide for yourself what these questions mean to you. But I believe that one thing is clear. Einstein showed that even though space and time can independently differ for different observers, the four-dimensional space-time reality is the same for everyone.

This implies that events in space-time have a permanence to them that cannot be taken away. Once an event occurs, in essence it becomes part of the fabric of our universe. Every human life is a series of events, and this means that when we put them all together, each of us is creating our own, indelible mark on the universe. Perhaps if everyone understood that, we might all be a little more careful to make sure that the mark we leave is one that we are proud of.

So there you have it. Relativity is necessary to comprehend the universe as we know it, it helps us understand the potential we all share when we put our brains to work for the common good, and if we all understood it we might treat each other a little more kindly.

By Gregory Walton

Radical new research led by a British scientist has suggested that there may be a second universe where time runs backwards.

The theoretical claims put forward in the Physical Review Letters journal could revolutionise the field of research into the origin and future of the universe.

In the paper titled ‘Identification of a Gravitational Arrow of Time’, an international team of world renowned scientists led by Oxfordshire-based Dr Julian Barbour challenge assumptions about the so called ‘arrow of time’.

The ‘arrow of time’ is the theory that time is symmetric and therefore time moves forward. They contend that there is no scientific reason that a mirror universe could not have been created where time moved in an distinct way from our own.

But in a quirk of science it is thought that if a parallel universe did exist where time moved backward, any sentient beings there would consider that time in our universe in fact moved backward.

The arrow of time is also known as the ‘one-way’ direction of time and was devised by a British scientist, Dr Arthur Eddington, in the twenties.

All of the laws of physics apply no matter which way time is moving and therefore there is no scientific impediment to such a parallel universe.

Dr. Barbour says: “Time is a mystery. Basically, all the known laws of physics look exactly the same whichever way time runs, and in the world in which we live in everything goes in one direction.”

“If you look at a simple model with a swarm of bees in the middle of the Big Bang but breaking up in either direction, then you would say there are two arrows of time, pointing in opposite direction from the swarm. One arrow would be forwards and one backwards.”

However Dr Barbour acknowledges that locating the ‘other’ universe in practical terms is an altogether different question.

“Our results are a proof of principle,” he said.